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 A212021 Number of (w,x,y,z) with all terms in {1,...,n} and 2w*x=3*y*z. 2
 0, 0, 0, 8, 16, 20, 48, 56, 80, 132, 164, 176, 272, 288, 332, 436, 512, 532, 696, 720, 844, 1000, 1076, 1104, 1360, 1430, 1518, 1758, 1942, 1978, 2328, 2368, 2566, 2818, 2938, 3098, 3600, 3648, 3780, 4084, 4440, 4492, 4996, 5052, 5348, 5920 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS Each term is divisible by 2.  See A211795 for a guide to related sequences. LINKS MATHEMATICA t = Compile[{{n, _Integer}}, Module[{s = 0}, (Do[If[2 w*x == 3 y*z, s = s + 1], {w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]]; Map[t[#] &, Range[0, 50]] (* A212021 *) %/2  (* integers *) (* Peter J. C. Moses, Apr 13 2012 *) CROSSREFS Cf. A211795. Sequence in context: A114435 A327092 A112679 * A096912 A254141 A188438 Adjacent sequences:  A212018 A212019 A212020 * A212022 A212023 A212024 KEYWORD nonn AUTHOR Clark Kimberling, Apr 28 2012 STATUS approved

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Last modified May 27 03:13 EDT 2022. Contains 354093 sequences. (Running on oeis4.)